solar cells

Abstract

One aspect of the present invention aims to provide a solar cell with high energy conversion efficiency. [Solution] One aspect of the present invention relates to a solar cell comprising, in the stacking direction, a transparent substrate, a first electrode layer made of a transparent conductive material, a photoelectric conversion layer mainly composed of an organic-inorganic perovskite compound, a second electrode layer, and an anti-reflective layer between the substrate and the first electrode layer containing nanoparticles with an average particle size of 100 nm or less.

Description

[Technical Field]

[0001] One aspect of the present invention relates to a solar cell. [Background technology]

[0002] One type of solar cell known is the perovskite solar cell, in which the main component of the photoelectric conversion layer is a perovskite compound.

[0003] As an example of a perovskite solar cell, Patent Document 1 describes a perovskite solar cell comprising a transparent conductive support, an electron blocking layer, a perovskite layer, an electron transport layer, a hole blocking layer, and a back electrode, wherein both the electron blocking layer and the hole blocking layer contain inorganic materials. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2017 / 073472 [Overview of the project] [Problems that the invention aims to solve]

[0005] There is a need for solar cells with high energy conversion efficiency that can efficiently convert incoming sunlight into electricity.

[0006] Therefore, one aspect of the present invention aims to provide a solar cell with high energy conversion efficiency. [Means for solving the problem]

[0007] The inventors have discovered that by arranging nanoparticles between a substrate and a transparent electrode layer in a solar cell, the energy conversion efficiency of the resulting solar cell is improved, and have completed one aspect of the present invention.

[0008] In other words, the gist of one aspect of the present invention is as follows: (1) A solar cell comprising, in the stacking direction, a transparent substrate, a first electrode layer made of a transparent conductive material, a photoelectric conversion layer mainly composed of an organic inorganic perovskite compound, a second electrode layer, and an anti-reflective layer between the substrate and the first electrode layer containing nanoparticles with an average particle size of 100 nm or less. (2) The solar cell according to (1), wherein the substrate is flexible and has a striped structure in which regions where the anti-reflective layer is not formed and regions where the anti-reflective layer is formed alternately appear in a direction perpendicular to the stacking direction. (3) The solar cell according to (2), wherein the substrate has curvature, and the direction in which the striped structure of the anti-reflective layer appears is the same as the direction in which the curvature appears. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a solar cell with high energy conversion efficiency. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view showing an example of the structure in the stacking direction of a solar cell according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing a perovskite crystal structure. [Figure 3] This figure schematically shows the configuration of a solar cell according to one embodiment of the present invention, in a direction perpendicular to the stacking direction. [Modes for carrying out the invention]

[0011] A preferred embodiment of one aspect of the present invention will be described in detail below. In this specification, the features of one aspect of the present invention will be described with reference to the drawings as appropriate. In the drawings, the dimensions and shapes of each part are exaggerated for clarity and do not accurately depict the actual dimensions and shapes. Therefore, the technical scope of one aspect of the present invention is not limited to the dimensions and shapes of each part shown in these drawings. Note that the solar cell of one aspect of the present invention is not limited to the following embodiments, and can be implemented in various forms with modifications, improvements, etc. that can be made by those skilled in the art without departing from the gist of one aspect of the present invention.

[0012] One aspect of the present invention relates to a solar cell including a photoelectric conversion layer containing an organic-inorganic perovskite compound as a main component.

[0013] The solar cell of one aspect of the present invention includes an antireflection layer containing nanoparticles having an average particle diameter of 100 nm or less between a transparent substrate and a first electrode layer made of a transparent conductive material.

[0014] Since the solar cell of one aspect of the present invention includes an antireflection layer containing nanoparticles, reflection of incident sunlight at the substrate / electrode layer interface is suppressed, the amount of incident sunlight on the photoelectric conversion layer is increased, and as a result, the energy conversion efficiency can be improved. That is, by arranging an antireflection layer containing nanoparticles, the reflectance can be reduced and the power generation efficiency can be improved. Further, by providing the antireflection layer between the substrate and the first electrode layer instead of on the surface of the solar cell, the influence of surface contamination and friction can be avoided and a decrease in durability can be suppressed.

[0015] [[ID=A16]]<Configuration in the stacking direction of the solar cell> First, the structure of the solar cell of one aspect of the present invention will be described in detail. FIG. 1 is a schematic cross-sectional view showing an example of the structure in the stacking direction of the solar cell of one aspect of the present invention.

[0016] As shown in FIG. 1, in one embodiment, the solar cell C of one aspect of the present invention has a substrate 1, an antireflection layer N, a first electrode layer 2a, a first carrier transport layer 3a, a photoelectric conversion layer 4, a second carrier transport layer 3b, and a second electrode layer 2b in this order.

[0017] (Anti-reflection layer N) The anti-reflective layer N is a layer located between the substrate 1 and the first electrode layer 2a. The nanoparticles used to form the anti-reflective layer N may be composed of the same transparent conductive material as the transparent conductive material used to form the first electrode layer 2a, or they may be composed of an insulating material such as glass. The anti-reflective layer N suppresses the reflection of sunlight incident on the solar cell C at the substrate 1 / first electrode layer 2a interface.

[0018] More specifically, sunlight incident on solar cell C is less likely to be reflected toward the outside world (i.e., toward the incident sunlight) at the substrate 1 / first electrode layer 2a interface by the anti-reflective layer N, and is more likely to be transmitted toward the photoelectric conversion layer 4.

[0019] The average particle size of the nanoparticles in the anti-reflective layer N is 100 nm or less, in one embodiment 80 nm or less, in one embodiment 60 nm or less, in one embodiment 40 nm or less, and in one embodiment 20 nm or less. The lower limit of the average particle size of the nanoparticles in the anti-reflective layer N is not limited. The average particle size of the nanoparticles in the anti-reflective layer N is usually 1 nm or more, in one embodiment 2 nm or more, in one embodiment 3 nm or more, in one embodiment 4 nm or more, and in one embodiment 5 nm or more. Here, the average particle size of the nanoparticles can be measured by dynamic light scattering (DLS). By reducing the average particle size of the nanoparticles in the anti-reflective layer N, the formation of irregularities on the surface of the first electrode layer 2a can be suppressed, and reflection of sunlight at the interface can be further suppressed.

[0020] The thickness of the anti-reflective layer N is typically in the range of 1 nm to 200 nm, and in one embodiment, it is in the range of 20 nm to 100 nm.

[0021] (Photoelectric conversion layer 4) Returning to the explanation of Figure 1. The photoelectric conversion layer 4 is located between the first carrier transport layer 3a and the second carrier transport layer 3b. The photoelectric conversion layer 4 generates charge carriers by receiving light. The charge carriers generated in the photoelectric conversion layer 4 move to either the first carrier transport layer 3a or the second carrier transport layer 3b.

[0022] More specifically, the positive charge carriers, i.e., holes, generated in the photoelectric conversion layer 4 are transported to either the first electrode layer 2a or the second electrode layer 2b via the hole transport layer, whichever of the first carrier transport layer 3a and second carrier transport layer 3b corresponds to the first electrode layer 2a. Furthermore, the negative charge carriers, i.e., electrons, generated in the photoelectric conversion layer 4 are transported to either the first electrode layer 2a or the second electrode layer 2b via the electron transport layer, whichever of the first carrier transport layer 3a and the second carrier transport layer 3b is designated as the electron transport layer.

[0023] The photoelectric conversion layer 4 contains an organic-inorganic perovskite compound, and in one embodiment, the organic-inorganic perovskite compound is the main component. The content of the organic-inorganic perovskite compound in the photoelectric conversion layer 4 is usually 60% by weight or more, in one embodiment it is 80% by weight or more, in one embodiment it is 90% by weight or more, in one embodiment it is 95% by weight or more, and in one embodiment it is 100% by weight. The film thickness of the photoelectric conversion layer is typically in the range of 100 nm to 1000 nm, and in one embodiment, it is in the range of 400 nm to 700 nm.

[0024] Organic-inorganic perovskite compounds are compounds that have a perovskite-type crystal structure. Figure 2 is a schematic diagram showing a perovskite-type crystal structure. As shown in Figure 2, the perovskite-type crystal structure has a cubic unit cell, with A positioned at each vertex of the cubic crystal, B positioned at the body center, and X positioned at the center of each face of the cubic crystal with B at the center. The fact that a compound has a perovskite-type crystal structure can be confirmed, for example, by X-ray diffraction measurement.

[0025] Organic-inorganic perovskite compounds can be represented, for example, by the following formula (1). ABX3(1) (In the formula, A is a monovalent cation, including at least one organic cation, B is a divalent cation, and X is a monovalent anion.)

[0026] In one embodiment, in formula (1), A is at least one selected from a monovalent organic ammonium ion and a monovalent amidinium-based ion.) Examples of the monovalent organic ammonium ion include CH3NH3 + (methylammonium ion: MA), C2H5NH3 + , C3H7NH3 + and C4H9NH3 + etc. are included.) Examples of the monovalent amidinium-based ion include HC(NH2)2 + (formamidinium ion: FA).)

[0027] In one embodiment, in formula (1), A may further contain a monovalent metal ion. Examples of the monovalent metal ion include rubidium ion (Rb + ) and cesium ion (Cs + ).)

[0028] In formula (1), A may be a combination of a monovalent organic ammonium ion, a monovalent amidinium-based ion, and a monovalent metal ion. In one embodiment, in formula (1), A is MA or FA, or a combination of two selected from the group consisting of MA, FA, and Cs + . In one embodiment, in formula (1), A is a mixed cation of Cs + , MA, and FA. When A is a mixed cation, the mixing ratio of each cation is not limited.)

[0029] In one embodiment, in formula (1), B is a divalent metal ion, for example, lead ion (Pb 2+ ), tin ion (Sn 2+ ) and combinations thereof. In one embodiment, from the perspective of improving durability, B is Pb 2+ .)

[0030] In one embodiment, in formula (1), X is a halogen ion, for example, a fluoride ion (F - ), chloride ions (Cl - ), bromide ions (Br - ) and iodide ions (I - It is at least one selected from ). In one embodiment, in formula (1), X is Cl - , Br - and I - It is at least one selected from. In one embodiment, in formula (1), X is I - That is the case.

[0031] (First carrier transport layer 3a and second carrier transport layer 3b) Returning to the explanation of Figure 1. The first carrier transport layer 3a receives the charge carriers generated in the photoelectric conversion layer 4 and transports these charge carriers to the first electrode layer 2a. If the first carrier transport layer 3a is a hole transport layer (HTL), the first carrier transport layer 3a transports holes to the first electrode layer 2a. If the first carrier transport layer 3a is an electron transport layer (ETL), the first carrier transport layer 3a transports electrons to the first electrode layer 2a. A detailed explanation of the hole transport layer and electron transport layer will be provided later.

[0032] The second carrier transport layer 3b receives the charge carriers generated in the photoelectric conversion layer 4 and transports these charge carriers to the second electrode layer 2b. If the second carrier transport layer 3b is a hole transport layer, the second carrier transport layer 3b transports holes to the second electrode layer 2b. If the second carrier transport layer 3b is an electron transport layer, the second carrier transport layer 3b transports electrons to the second electrode layer 2b.

[0033] In the first embodiment, the first carrier transport layer 3a is an electron transport layer, and the second carrier transport layer 3b is a hole transport layer. That is, in the first embodiment, a solar cell C according to one aspect of the present invention has a substrate, an anti-reflective layer, a cathode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and an anode in the order described above.

[0034] Furthermore, in the second embodiment, the first carrier transport layer 3a is a hole transport layer, and the second carrier transport layer 3b is an electron transport layer. In other words, in the second embodiment, the solar cell C according to one aspect of the present invention has a substrate, an anti-reflective layer, an anode, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a cathode in the order described above.

[0035] The hole transport layer has the function of transporting holes generated by photoelectric conversion in the photoelectric conversion layer to the first electrode layer or the second electrode layer. As the material for the hole transport layer, known organic or inorganic materials suitable for use in hole transport layers can be used.

[0036] Organic materials that can be used as materials for the hole transport layer are not particularly limited, but include, for example, 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD), polyethylenedioxythiophene:polystyrene sulfonic acid (PEDOT:PSS), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 3PATAT-C3 (Non-patent literature: Journal of The American Chemistry Society 2023, No. 145, p. 7528), etc.

[0037] The inorganic materials that can be used as the material for the hole transport layer are not particularly limited, but include, for example, nickel oxide and copper oxide.

[0038] In one embodiment, in the first embodiment of the solar cell according to one aspect of the present invention, the material of the hole transport layer is one or more selected from the group consisting of Spiro-OMeTAD, PTAA, and nickel oxide. In one embodiment, in a second embodiment of the solar cell according to one aspect of the present invention, the material of the hole transport layer is one or more selected from the group consisting of PEDOT:PSS, PTAA, and nickel oxide.

[0039] The electron transport layer has the function of transporting electrons generated by photoelectric conversion in the photoelectric conversion layer to the first electrode layer or the second electrode layer. As the material for the electron transport layer, known organic or inorganic materials suitable for use in electron transport layers can be used.

[0040] Organic materials that can be used as materials for the electron transport layer are not particularly limited, but include, for example, fullerene compounds, phenanthroline derivatives (e.g., bathocuproine), polyethyleneimines, etc. Examples of fullerene compounds include fullerenes (e.g., C60 fullerene, C70 fullerene) and derivatives of fullerenes with substituents added (e.g., [6,6]-phenyl-C 61 -Methyl butyrate (also known as PCBM or

[60] PCBM), [6,6]-phenyl-C 71 Examples include methyl butyrate (also known as PCBM or

[70] PCBM)).

[0041] Inorganic materials that can be used as materials for electron transport layers include titanium oxide, tin oxide, and zinc oxide.

[0042] In one embodiment, in the first embodiment of the solar cell according to one aspect of the present invention, the material of the electron transport layer is one or more selected from the group consisting of fullerene, PCBM, bathocuproine, polyethyleneimines, titanium dioxide, and tin oxide. In one embodiment, in a second embodiment of the solar cell according to one aspect of the present invention, the material of the electron transport layer is one or more selected from the group consisting of fullerenes, PCBM, bathocuproine, and polyethyleneimines.

[0043] (First electrode layer 2a and second electrode layer 2b) The first electrode layer 2a is the electrode in contact with the first carrier transport layer 3a. When the first carrier transport layer 3a is a hole transport layer, the first electrode layer 2a becomes the anode, and when the first carrier transport layer 3a is an electron transport layer, the first electrode layer 2a becomes the cathode. The second electrode layer 2b is the electrode in contact with the second carrier transport layer 3b. When the second carrier transport layer 3b is a hole transport layer, the second electrode layer 2b becomes the anode, and when the second carrier transport layer 3b is an electron transport layer, the second electrode layer 2b becomes the cathode.

[0044] The first electrode layer 2a is a transparent electrode layer, and as the material for the transparent electrode layer, transparent conductive films such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide (FTO) can be used.

[0045] As the material for the second electrode layer 2b, metal materials such as aluminum (Al), silver (Ag), and gold (Au), transparent conductive films such as ITO, IZO, AZO, and FTO, and carbon nanotubes, as well as other materials known as electrodes for solar cells, can be used.

[0046] In one embodiment, the materials of the first electrode layer 2a and the second electrode layer 2b are ITO, IZO, and FTO.

[0047] In one embodiment, the film thickness of the first electrode layer 2a and the second electrode layer 2b is typically in the range of 100 nm to 300 nm.

[0048] (Circuit board 1) The substrate 1 is a plate-shaped or film-shaped member that supports an anti-reflective layer N, a first electrode layer 2a, a first carrier transport layer 3a, a photoelectric conversion layer 4, a second carrier transport layer 3b, and a second electrode layer 2b.

[0049] Substrate 1 is a transparent substrate. As a transparent substrate, a substrate made of one or more materials selected from inorganic materials such as glass, or organic materials such as polyethylene, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamide-imide, liquid crystal polymer, or cycloolefin polymer can be used.

[0050] In one embodiment, the substrate 1 is made of a flexible material. Here, "flexibility" means the property of bending flexibly under external force, that is, it means being flexible and resistant to breaking even when bent. The flexible substrate 1 allows it to be installed on curved surfaces when mounted in a vehicle, and by making the anti-reflective layer a striped structure as described below, cracks when bent can be reduced.

[0051] <Configuration perpendicular to the stacking direction of the solar cells> Figure 3 schematically shows the configuration of a solar cell C according to one embodiment of the present invention in a direction perpendicular to the stacking direction. In a solar cell according to one embodiment of the present invention, in a direction perpendicular to the stacking direction, regions where the anti-reflective layer N is not formed (width R) and regions where the anti-reflective layer N is formed (width S) appear alternately, forming a striped (patterned) structure.

[0052] In one embodiment of the present invention, the solar cell C has curvature, and the direction in which the striped structure of the anti-reflective layer N appears is the same as the direction in which the curvature appears, in a direction perpendicular to the stacking direction. Therefore, in one embodiment of the present invention, the direction perpendicular to the stacking direction is also called the curved surface direction.

[0053] A solar cell C according to one embodiment of the present invention having such a structure can prevent cracks from occurring in the anti-reflective layer N when used on a curved surface, for example, when used as an on-board panel type solar cell for mounting on the roof of an automobile.

[0054] In one embodiment, the ratio of width R to width S (R / S) in the striped structure formed by the presence or absence of the anti-reflective layer N is not particularly limited, but is usually in the range of 0.01 to 1, and in one embodiment, it is in the range of 0.1 to 0.5.

[0055] By keeping the ratio of width R to width S within the aforementioned range, the solar cell C can ensure the suppression effect of the anti-reflective layer N in reducing sunlight reflection while preventing cracks from forming in the anti-reflective layer N when used on a curved surface.

[0056] A solar cell according to one aspect of the present invention can be used alone or in combination with other solar cells such as silicon (Si) solar cells. When used in combination with other solar cells, for example, a tandem solar cell can be formed in which another solar cell is laminated on the second electrode layer (the electrode opposite the substrate) side of the solar cell according to one aspect of the present invention.

[0057] <Method of manufacturing solar cells> Next, a method for manufacturing solar cells, that is, a manufacturing method according to one embodiment of the present invention, will be described in more detail. In the manufacturing method according to this embodiment, a solar cell is manufactured by depositing an anti-reflective layer N, a first electrode layer 2a, a first carrier transport layer 3a, a photoelectric conversion layer 4, a second carrier transport layer 3b, and a second electrode layer 2b on a substrate 1 in the order described above. The manufacturing method according to this embodiment is characterized in that, on the surface where the substrate 1 and the transparent electrode layer which is the first electrode layer 2a are in contact, an area where the anti-reflective layer N is not to be formed is masked, and a dispersion liquid containing nanoparticles is applied only to the area where the anti-reflective layer N is to be formed, thereby depositing the anti-reflective layer N. The film deposition process for the remaining parts can be the same as that used for conventional photoelectric conversion elements (solar cells). Other manufacturing methods according to this embodiment include a coating method that allows for pattern coating such as inkjet, and a method in which a layer is formed by coating and then only a predetermined area is removed by laser scribing or the like.

[0058] The dispersion containing nanoparticles can be applied to the substrate 1 by known methods. The application method for the dispersion containing nanoparticles is not particularly limited and includes, for example, spin coating, inkjet, spray, blade coating, and die coating.

[0059] Dispersions containing nanoparticles can typically be applied in air at temperatures between 15°C and 35°C.

[0060] As nanoparticles, transparent conductive materials such as ITO, IZO, AZO, and FTO, and insulating materials such as glass can be used. In one embodiment, the average particle size of the nanoparticles is 100 nm or less, in one embodiment 80 nm or less, in one embodiment 60 nm or less, in one embodiment 40 nm or less, and in one embodiment 20 nm or less. The lower limit of the average particle size of the nanoparticles is not limited. The average particle size of the nanoparticles is usually 1 nm or more, in one embodiment 2 nm or more, in one embodiment 3 nm or more, in one embodiment 4 nm or more, and in one embodiment 5 nm or more. Here, the average particle size of the nanoparticles can be measured by dynamic light scattering (DLS). By reducing the average particle size of the nanoparticles, the formation of irregularities on the surface of the first electrode layer can be suppressed, and the reflection of sunlight at the interface can be further suppressed.

[0061] The concentration of nanoparticles in the dispersion containing nanoparticles is not particularly limited, but is usually 5% by weight or less, and in one embodiment, 3% by weight or less, relative to the total weight of the dispersion. By setting the nanoparticle concentration to the above concentration, the reflection of incident sunlight can be suppressed, and the transmission of sunlight to the photoelectric conversion layer of the solar cell and the absorption of sunlight by the photoelectric conversion layer can be improved.

[0062] The solvent for the dispersion containing nanoparticles is an alcohol, such as isopropyl alcohol (iPA). By using an alcohol as the solvent for the dispersion containing nanoparticles, the degradation of the photoelectric conversion layer and the carrier transport layer can be suppressed.

[0063] A manufacturing method according to one embodiment of the present invention may include a step of drying a dispersion containing coated nanoparticles. The drying step can usually be carried out by heating in a range of 80°C to 150°C.

[0064] In one embodiment of the present invention, the layers other than the anti-reflective layer can be formed by depositing a film using a known method. In one embodiment, the ITO used in the electrode layer, such as the first electrode layer, can be deposited by sputtering. [Explanation of Symbols]

[0065] 1: Circuit board 2a: First electrode layer 2b: Second electrode layer 3a: First carrier transport layer 3b: Second carrier transport layer 4: Photoelectric conversion layer N: Anti-reflection layer C: Solar battery

Claims

1. In the stacking direction, A transparent substrate and A first electrode layer made of a transparent conductive material, A photoelectric conversion layer containing an organic-inorganic perovskite compound as the main component, The second electrode layer and An anti-reflective layer between the substrate and the first electrode layer, comprising nanoparticles with an average particle size of 100 nm or less, Solar cells, including

2. The solar cell according to claim 1, wherein the substrate is flexible and has a striped structure in which regions where the anti-reflective layer is not formed and regions where the anti-reflective layer is formed alternately appear in a direction perpendicular to the stacking direction.

3. The solar cell according to claim 2, wherein the substrate has curvature, and the direction in which the striped structure of the anti-reflective layer appears is the same as the direction in which the curvature appears.

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